Permanent magnet solenoid device

ABSTRACT

A pair of substantially identical high powered cylindrical magnets are arranged in axially aligned opposing relation in a cylindrical casing of non-magnetic material, with their facing ends spaced axially from each other. Each permanent magnet has a central cylindrical pole of one polarity, an annular pole of the opposite polarity and a base interconnecting its poles at the end remote from the other permanent magnet and forming the base of an open annular groove separating its two poles. An inner circular pole piece is interposed between the facing ends of the two cylindrical poles, and an outer annular pole piece is interposed between the facing ends of the annular poles, the two pole pieces defining an annular air gap having a very small radial dimension. A cylindrical winding form, of non-magnetic material and carrying a winding, is movably positioned substantially symmetrically in the air gap. A plurality, such as three, of angularly spaced pins of non-magnetic metal are connected to the winding form and extend outwardly through the annular groove of one permanent magnet and through dielectric bushings in the apertures in the base thereof. A fourth pin, constituting an electric conductor, terminates short of the winding form and is electrically connected at its inner end to one terminal of the winding and extends outwardly through a bushing in the base of the one permanent magnet for connection to a terminal of a source of electric potential. All of the pins, except the fourth pin, have their outer ends secured to a thin brass plate which is secured to a central pin or operator in turn secured centrally to a flexible diaphragm and projecting outwardly through an opening in the casing of the device. The fourth pin extends through the brass plate, with clearance. The air gap has a dimension of from 0.010 to 0.020 inches and, when the winding is energized, the operator will move 8 ounces through 0.1 inch with 6 millijoules of energy. The device is used as a trigger for missiles.

United States Patent [191 Ludwig et al.

14 1 Jan. 15, 1974 PERMANENT MAGNET SOLENOID DEVICE [75] Inventors: JohnT. Ludwig, Jacksonville; Paul D. Steiner, Clearwater, both of Fla.

[73] Assignee: Electromagnetic Industries, Inc.,

Clearwater, Fla.

[22] Filed: Oct. 27, 1972 [21] Appl. No.: 301,315

[52] U.S. Cl 335/231, 335/222 [51] Int. Cl. HOlf 7/08 [58] Field ofSearch 335/222, 223, 231

[56] References Cited UNITED STATES PATENTS 3,013,189 12/1961 Bernier335/231 Primary Examiner-George Harris Attorney-John J. McGlew et a1.

[57] ABSTRACT A pair of substantially identical high powered cylindricalmagnets are arranged in axially aligned opposing relation in acylindrical casing of non-magnetic material, with their facing endsspaced axially from each other. Each permanent magnet has a centralcylindrical pole of one polarity, an annular pole of the oppositepolarity and a base interconnecting its poles at the end remote from theother permanent magnet and forming the base of an open annular grooveseparating its two poles. An inner circular pole piece is interposedbetween the facing ends of the two cylindrical poles, and an outerannular pole piece is interposed between the facing ends of the annularpoles, the two pole pieces defining an annular air gap having a verysmall radial dimension. A cylindrical winding form, of non-magneticmaterial and carrying a winding, is movably positioned substantiallysymmetrically in the air gap. A plurality, such as three, of angularlyspaced pins of non-magnetic metal are connected to the winding form andextend outwardly through the annular groove of one permanent magnet andthrough dielectric bushings in the apertures in the base thereof. Afourth pin, constituting an electric conductor, terminates short of thewinding form and is electrically connected at its inner end to oneterminal of the winding and extends outwardly through a bushing in thebase of the one permanent magnet for connection to a terminal of asource of electric potential. All of the pins, except the fourth pin,have their outer ends secured to a thin brass plate which is secured toa central pin or operator in turn secured centrally to a flexiblediaphragm and projecting outwardly through an opening in the casing ofthe device. The fourth pin extends through the brass plate, withclearance. The air gap has a dimension of from 0.010 to 0.020 inchesand, when the winding is energized, the operator will move 8 ouncesthrough 0.1 inch with 6 millijoules of energy. The device is used as atrigger for missiles.

10 Claims, 4 Drawing Figures Wmmn 3786 383- sman 1 OF 2 I FIG-IPATENIEDJAUS 1924 3786383 SHEET 2 0f 2 1 PERMANENT MAGNET SOLENOIDDEVICE BACKGROUND OF THE INVENTION There are many applications where itis required that a high force, acting through a short distance, must beprovided with a minimum of input or energy, such as electrical energy.Among such applications are trigger devices for missiles where lowweight is essential and where a very high capacity source of electricpotential is not available.

SUMMARY OF THE INVENTION This invention relates to permanent magnetsolenoid devices and, more particularly, to a novel, improved, compactand simplified permanent magnet solenoid device capable of exerting,when energized, a high force through a small distance and with a minimumconsumption of electrical energy.

In accordance with the invention, a pair of high power substantiallyidentical cylindrical permanent magnets are arranged in axially alignedand spaced opposing relation in a close fitting housing of nonmagneticmaterials such as, for example, a plastic composition material.Preferably, the housing is cup-shaped having a diametrically extendingbottom wall which is preferably integral with its cylindrical side wall.The other end of the housing is arranged to be closed by a cover havinga central aperture therethrough and arranged to be sealed to the sidewall of the housing.

Each permanent magnet has a central cylindrical pole of one polarity,such as a north polarity, and an annular pole of the opposite polarity,such as a south p'olarity, and is formed integrally with a baseinterconnecting its poles at the end remote from the other permanentmagnet. Thus, for example, the base of one magnet seats against theclosed bottom wall of the housing, and the base of the other magnet isadjacent the initially open end of the housing. The bases of the magnetsform the bases of respective open annular grooves separating the twopoles of the associated magnet, these grooves widening from the base ofthe magnet toward the other end thereof. For a purpose to be described,the base of each magnet is formed with a plurality of aperturestherethrough arranged in equiangular spaced relation at the bottom ofeach annular groove.

A substantially flat inner circular pole piece is inter-- posed betweenand in engagement with the facing ends of the cylindrical magnet poles,and has an annular shoulder embracing these poles so that, in diametriccross section, the inner circular pole piece has an I- beam shape withbeveled outer surfaces. A substantially flat outer annular pole piece isinterposed between the facing ends of the annular poles, having an outerdiameter equal to that of the two permanent magnets and having aradially inner shoulder thereon seating into the two facing annulargrooves in the magnets. The two pole pieces define therebetween anannular air gap having a very small radial dimension such as, forexample, an air gap of 0.10 0.20 inches.

A cylindrical bobbin or winding form, having flanges on its axiallyopposite ends, is seated in the air gap, and is formed of non-magneticmaterial such as, for example, brass. A moving coil type of winding iswound on this bobbin and preferably has one terminal electricallyconnected to the bobbin for connection to an external ground. Threeequally angular spaced pins of nonmagnetic material, such as brass orthe like, are mechanically secured to one flange of the bobbin andextend through insulating bushings seated in the apertures in the baseof the permanent magnet adjacent the initially open end of the casing,and through apertures in a dielectric guide ring adjacent their innerends. These pins have a close conforming fit through equally angularspaced apertures in an outer guide or positioning ring of non-magneticmaterial such as, for example, plastic composition material. Theelectrical connection to the opposite terminal of the winding on thebobbin is effected by soldering or brazing the free end of the windingto an additional brass lead pin whose inner end sets into and terminatesat the inner guide ring. The two guide rings form a movable unit withthe brass pins.

A brass plate is secured to the outer ends of the three pins, and is inthe form of a circle having two equal segments cut therefrom to providechords extending at equal angles to a diameter of the circle. This brassplate is formed with three relatively small diameter threaded aperturesto receive the ends of the pins, and may be formed with a largeraperture, at the same radius as the pins, to receive, with clearance,the aforementioned lead pin. To decrease air resistance, the plate isformed with a number of relatively large diameter apertures.

The open end of the casing is formed with a seat for a sealing washerwhich consists of a relatively rigid plastic composition annular ring towhich is bonded a thin flexible diaphragm formed preferably of surgicallatex rubber. This diaphragm has a central aperture therein bounded byan O-ring which is bonded to the diaphragm. A metal operator, in theform of a substantially cylindrical plunger, is secured to the brassplate by a screw or the like threaded into an aperture in the plunger,and the plunger extends, with slight clearance through the O-ring andoutwardly through an aperture in the cover which is sealed to the openend of the cylindrical casing after assembly of the device. The outerend of the plunger may have a threaded aperture, and the plunger mayhave flattened sides for securing a trigger or link to the plunger foroperation by the solenoid.

An object of the'invention is to provide an improved permanent magnetsolenoid device.

Another object of the invention is to provide such a solenoid devicewhich is capable of exerting a great force through a small distance,when energized.

A further object of the invention is to provide such a device whichrequires only a very small amount of electrical energy for itsoperation.

Another object of the invention is to provide such a device whichcomprises a pair of identical permanent magnets having pole piecesinserted between their facing ends and defining a very small air gapreceiving a moving coil type of winding connected mechanically to anoperator.

A further object of the invention is to provide such a device which issmall, compact, efficient and inexpensive, and which is well adapted foruse in operating the trigger of a missile, for example.

For an understanding of the principles of the invention, reference ismade to the following description of a typical embodiment thereof asillustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. I is an exploded view of a permanent magnet solenoid deviceembodying the invention;

FIG. 2 is an axial sectional view through the device;

FIG. 3 is a diametric sectional view taken on the line 3-3 of FIG. 2;and

FIG. 4 is a diametric sectional view taken on the line 4-4 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, thepermanent magnet solenoid device embodying the invention is mountedwithin a casing having a cylindrical side wall 11 and a bottom wall 12closing one end of the casing and preferably integral with side wall 11.The open end of the casing is formed with an annular shoulder 13, andcasing 10 has mounting flanges 14 formed with suitable apertures forsecuring the casing in position. After assembly of the severalcomponents of the device within casing 10, the casing is sealed by acover 15 which has a shoulder 16 mating with the shoulder 13 and isformed with a central aperture 17 for a purpose to be described.

The essential components of the device include a pair of identicalpermanent magnets and 20', of high magnetic power, which cooperate,through pole pieces to be described hereinafter, with a moving coilwinding 38 wound on a bobbin 35. As the two permanent magnets areidentical, only the permanent magnet 20 will be described in detail. Themagnet 20' is seated on a plate 18 in turn seated on bottom wall 12 ofcasing 10, plate 18 being made of non-magnetic material such as, forexample, a plastic composition material.

Magnets 20 and 20' are arranged in facing relation within casing 10, andhave a very close fit therein, with magnet 20 being adjacent wall 12 andmagnet 20 being adjacent the open end of casing 10. Permanent magnet 20has a central cylindrical pole 21 and an annular outer pole 22, the twopoles being of opposite polarity with pole 21 preferably being a northpole and pole 22 preferably being a south pole. The two poles areinterconnected by a base 23, forming part of the magnetic circuit, anddefine between them an annular groove 24 which increases in radialdimension outwardly from base 23. Base 23 is formed with a series ofequally angular spaced apertures 26, such as, for example, six aperturesat 60 spacing from each other. Permanent magnet 20' is identical inconstruction with permanent magnet 20.

Within casing 10, permanent magnets 20 and 20' are arranged in axiallyspaced relation to receive therebetween an inner or north circular polepiece 25 and an outer or south annular pole piece 30. The axialthicknesses of pole pieces 25 and are substantially identical, and polepiece 25 is formed with a peripheral rib 27 closely embracing andconforming to pole pieces 21 and 21 The surfaces of rib 27 are beveledas indicated at 28. Pole piece 30 has an outer diameter equal to theouter diameter of permanent magnets 20 and 20 and an inner diameter ofcylindrical wall of casing 10. Pole piece 30 is formed with an innerannular rib 31 which closely and conformingly engages the radial innersurfaces of annular poles 22 and 22'. Pole pieces 25 and 30 define avery small air gap 33 which may be 0.010 0.020 inches in radialdimension. A cylindrical bobbin or winding form 35, of non-magneticmaterial such as brass or the like, is arranged in air gap 33 andcarries a moving coil winding 38 disposed between an upper flange 36 anda lower flange 37. Flange 36 is substantially wider radially than flange37, and is formed with a series of equal angularly spaced apertures eachreceiving an elongated brass pin 40 which is brazed or soldered toflange 36. In the illustrated example, there are three pins 40 arrangedat angular spacings of 60A fourth pin 40' serves as a lead for winding38, but is not connected electrically to winding form 35. One terminalof winding 38 is secured to winding form 35, and the other terminal issecured to pin 40'.

As viewed in FIG. 2, pins 40 extend upwardly from form 35 and with aclose fit through apertures in a guide ring 41 of non-magnetic material,such as a plastic composition material. The pins 40 then extend throughapertures 26 of permanent magnet 20 and through insulating bushings 42seated in these apertures and then through apertures in an insulating ordielectric ring 43. The upper ends of pins 40 are threaded intoapertures 46 located at equal angular intervals in a truncated circularbrass plate 45. Brass plate 45 is truncated by severing two circularsegments therefrom, with the chords of these segments being equal inlength and extending at equal angles to a diameter of plate 45. Afurther and much larger aperture 47 is provided for the passage of leadpin 40' through plate 45, the inner end of pin 40 being fixed to andterminating at ring 41. To reduce air resistance, brass plate 45 isformed with a series, such as six, of relatively large diameterapertures 48.

A sealing washer 50 is seated on shoulder 13 of casing 10, and heldseated on the shoulder by the shoulder 16 of cover 15 when cover 15 issealed to casing 10. Sealing washer 50 comprises a ring 51 of plasticcomposition material to the undersurface of which is sealed a diaphragm52 of surgical latex rubber, having a central aperture 53 surrounded byan O-ring 54 sealed to diaphragm 52. The lower end of operator 55 has athreaded aperture receiving a screw 56 extending through a centralaperture in brass plate 45. Operator 55 is secured to move withdiaphragm 52 of sealing washer 50 by virtue of a sealing meansinterconnecting operator 55 to O-ring 54. The outer end of operator 55extends outwardly through the aperture 17 in cover 15, with some littleclearance, and has a threaded aperture 57 whereby suitable mechanicallinkage or the like may be secured to operator 55. Such securing is alsofacilitated by the provision of flats 58 on the otherwise cylindricaloperator 55.

When a potential is applied to winding 38, the winding is energized and,in cooperation with the magnetic field produce across air gap 33 betweeninner and outer pole pieces 25 and 30, respectively, by permanentmagnets 20 and 20, effects an axial displacement of bobbin 35, pins 40,brass plate 45 and operator 55 to perform a desired mechanical functionsuch as, for example the triggering of a missile. In actual practice,the supply of six millijoules of electrical energy to winding 38 willmove eight ounces through 0.1 inch. The device is compact and itoperating parts are sealed against the ambient influences, with onlyleads for energizing winding 38 being brought into the casing 10 sealedby cover 15.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

l. A permanent magnet solenoid device comprising, in combination, a pairof substantially identical permanent magnet means arranged in axiallyaligned and axially spaced opposing relation, each permanent magnetmeans including a central cylindrical pole of one polarity and anannular pole of the opposite polarity form ing, with the central pole,an open annular groove separating the two poles; and inner substantiallycircular pole piece interposed between the facing ends of saidcylindrical poles; an outer annular pole piece interposed between thefacing ends of said annular poles; said inner and outer pole piecesdefining therebetween an annular air gap having a very small radialdimension;

a substantially cylindrical moving coil winding means positioned in saidair gap; a mechanical operator connected to said winding means for axialmovement with the latter; and circuit means connected to said windingmeans to apply an electric potential thereacross to effect axialmovement of said winding means and said operator.

2. A permanent magnet solenoid device, as claimed in claim 1, in whichsaid pair of substantially identical permanent magnet means comprises apair of substantially identical cylindrical permanent magnets eachhaving a base interconnecting its central and annular poles at the endsof the permanent magnet remote from the other permanent magnet, andforming the base of an open annular groove separating its two poles; andconnecting means interconnecting said winding means and said operatorand extending through the annular groove and through apertures in thebase of one of said permanent magnets; said operator being locatedaxially outwardly of said one permanent magnet.

3. A permanent magnet solenoid device, as claimed in claim 2, in whichsaid winding means comprises a winding form of non-magnetic material anda moving coil winding wound on said form; said connecting meansincluding pins of non-magnetic material connected to said winding formand extending outwardly through apertures in the base of said onepermanent magnet, and including means interconnecting the outer ends ofsaid pins and connected to said operator.

4. A permanent magnet solenoid device, as claimed in claim 3, in whichsaid winding form and said pins are formed of electrically conductive,non-magnetic metal; a ring of dielectric material positioned axiallyadjacent said winding form and having apertures closely embracing saidpins; a further pin secured to said ring and terminating thereat, saidfurther pin extending outwardly through an aperture in the base of saidone permanent magnet; one terminal of said winding being electricallyconnected to said winding form and the other terminal of said windingbeing electrically connected to said further pin.

5. A permanent magnet solenoid device, as claimed in claim 4, includinga cylindrical casing closely enbracing said permanent magnets and saidouter annular pole piece, and having a closed bottom wall seating thebase of the other of said permanent magnets, said casing having an openouter end; and a cover enclosing said open outer end of said casing andsealed to said casing; said cover being formed with an aperture and saidoperator extending outwardly through said cover aperture.

6. A permanent magnet solenoid device, as claimed in claim 5, in whichsaid pins extend through dielectric bushings seated in the apertures ofthe base of said one permanent magnet.

7. A permanent magnet solenoid device, as claimed in claim 6, includinga dielectric guide ring adjacent the outer surface of the base of saidone permanent magnet and formed with apertures through which said pinsextend.

8. A permanent magnet solenoid device, as claimed in claim 5, in whichsaid means interconnecting the outer ends of said pins comprises a plateof electrically conductive material; the open outer end of said casingbeing formed with an annular shoulder on its inner surface; and asealing washer seated in said annular shoulder and including a sealingdiaphragm having a central aperture therethrough; said operatorcomprising a substantially cylindrical metal member having its inner endsecured to said electrically conductive plate and extending through theaperture in said diaphragm and the aperture in said cover; said operatorbeing sealed to said flexible diaphragm at said aperture therein.

9. A permanent magnet solenoid device, as claimed in claim 8, in whichsaid sealing washer comprises a relatively rigid ring of dielectricmaterial seated in said annular shoulder; said diaphragm comprising athin sheet of elastomeric material stretched across and sealed to saidlast-named dielectric ring; and an O-ring sealed to said diaphragmconcentrically with the opening therein and sealed to said operator.

10. A permanent magnet solenoid device, as claimed in claim 9, in whichthe outer end of said operator is formed for mechanical connection tomeans operated by said device.

1. A permanent magnet solenoid device comprising, in combination, a pairof substantially identical permanent magnet means arranged in axiallyaligned and axially spaced opposing relation, each permanent magnetmeans including a central cylindrical pole of one polarity and anannular pole of the opposite polarity forming, with the central pole, anopen annular groove separating the two poles; an inner substantiallycircular pole piece interposed between the facing ends of saidcylindrical poles; an outer annular pole piece interposed between thefacing ends of said annular poles; said inner and outer pole piecesdefining therebetween an annular air gap having a very small radialdimension; a substantially cylindrical moving coil winding meanspositioned in said air gap; a mechanical operator connected to saidwinding means for axial movement with the latter; and circuit meansconnected to said winding means to apply an electric potentialthereacross to effect axial movement of said winding means and saidoperator.
 2. A permanent magnet solenoid device, as claimed in claim 1,in which said pair of substantially identical permanent magnet meanscomprises a pair of substantially identical cylindrical permanentmagnets each having a base interconnecting its central and annular polesat the ends of the permanent magnet remote from the other permanentmagnet, and forming the base of an open annular groove separating itstwo poles; and connecting means interconnecting said winding means andsaid operator and extending through the annular groove and throughapertures in the base of one of said permanent magnets; said operatorbeing located axially outwardly of said one permanent magnet.
 3. Apermanent magnet solenoid device, as claimed in claim 2, in which saidwinding means comprises a winding form of non-magnetic material and amoving coil winding wound on said form; said connecting means includingpins of non-magnetic material connected to said winding form andextending outwardly through apertures in the base of said one permanentmagnet, and including means interconnecting the outer ends of said pinsand connected to said operator.
 4. A permanent magnet solenoid device,as claimed in claim 3, in which said winding form and said pins areformed of electrically conductive, non-magnetic metal; a ring ofdielectric material positioned axially adjacent said winding form andhaving apertures closely embracing said pins; a further pin secured tosaid ring and terminating thereat, said further pin extending outwardlythrough an aperture in the base of said one permanent magnet; oneterminal of said winding being electrically connected to said windingform and the other terminal of said winding being electrically connectedto said further pin.
 5. A permanent magnet solenoid device, as claimedin claim 4, including a cylindrical casing closely enbracing saidpermanent magnets and said outer annular pole piece, and having a closedbottom wall seating the base of the other of said permanent magnets,said casing having an open outer end; and a cover enclosing said openouter end of said casing and sealed to said casing; said cover beingformed with an aperture and said operator extending outwardly throughsaid cover aperture.
 6. A permanent magnet solenoid device, as claimedin claim 5, in which said pins extend through dielectric bushings seatedin the apertures of the base of said one permanent magnet.
 7. Apermanent magnet solenoid device, as claimed in claim 6, including adielectric guide ring adjacent the outer surface of the base of said onepermanent magnet and formed with apertures through which said pinsextend.
 8. A permanent magnet solenoid device, as claimed in claim 5, inwhich said means interconnecting the outer ends of said pins comprises aplate of electrically conductive material; the open outer end of saidcasing being forMed with an annular shoulder on its inner surface; and asealing washer seated in said annular shoulder and including a sealingdiaphragm having a central aperture therethrough; said operatorcomprising a substantially cylindrical metal member having its inner endsecured to said electrically conductive plate and extending through theaperture in said diaphragm and the aperture in said cover; said operatorbeing sealed to said flexible diaphragm at said aperture therein.
 9. Apermanent magnet solenoid device, as claimed in claim 8, in which saidsealing washer comprises a relatively rigid ring of dielectric materialseated in said annular shoulder; said diaphragm comprising a thin sheetof elastomeric material stretched across and sealed to said last-nameddielectric ring; and an O-ring sealed to said diaphragm concentricallywith the opening therein and sealed to said operator.
 10. A permanentmagnet solenoid device, as claimed in claim 9, in which the outer end ofsaid operator is formed for mechanical connection to means operated bysaid device.